Some new designs of mobile communication devices—such as smart phones, tablet computers, and laptop computers—include two or more radio access technologies (“RATs”) that enable the devices to connect to two or more radio access networks. Examples of radio access networks include GSM, TD-SCDMA, CDMA2000, and WCDMA.
Some mobile communication devices that include a plurality of RATs may also include two or more radio-frequency communication circuits or “RF chains” to provide users with access to multiple separate networks simultaneously. For example, a mobile communication device that includes a plurality of Subscriber Identity Module (SIM) cards that are each associated with a different RAT and utilize a different RF resource to connect to a separate mobile telephony network is termed a “multi-SIM-multi-active” or “MSMA” communication device. An example MSMA communication device is a “dual-SIM-dual-active” or “DSDA” communication device, which includes two SIM cards/subscriptions associated with two mobile telephony networks.
When a mobile communication device includes a plurality of RATs, each RAT on the device may utilize a different RF chain to communicate with its associated network at any time. For example, a first RAT (e.g., a GSM RAT) may use a first transceiver to transmit to a GSM base station at the same time a second RAT (e.g., a WCDMA RAT) uses a second transceiver to transmit to a WCDMA base station. However, because of the proximity of the antennas of the RF chains included in a MSMA communication device, the simultaneous use of the RF chains may cause one or more RF chains to desensitize or interfere with the ability of the other RF chains to operate normally.
Generally, receiver desensitization (referred to as “de-sense”), or degradation of receiver sensitivity, may result from noise interference of a nearby transmitter. For example, when two radios are close together with one transmitting on the uplink—the aggressor communication activity (“aggressor”)—and the other receiving on the downlink—the victim communication activity (“victim”)—signals from the aggressor's transmitter may be picked up by the victim's receiver or otherwise interfere with reception of a weaker signal (e.g., from a distant base station). As a result, the received signals may become corrupted and difficult or impossible for the victim to decode. Receiver de-sense presents a design and operational challenge for multi-radio devices, such as MSMA communication devices, due to the necessary proximity of transmitters in these devices.